Polymer conjugates obtained by linking a physiologically active substance such as an anticancer agent or an anti-inflammatory agent, especially a physiologically active substance with low solubility in water, to a polymer carrier have been studied extensively as they are expected to be useful for improving the in vivo pharmacokinetics of the physiologically active substances themselves and the water solubility thereof and the like, and also for increasing the efficacy of the substances as drugs. Particularly, block copolymers in which a hydrophilic polymer and a hydrophobic polymer are bonded to each other may form a micelle having the hydrophobic polymer carrying a physiologically active substance as the inner shell and the hydrophilic polymer covering the surface of the inner shell. The block copolymer are characterized by being capable of maintaining the water solubility as the whole polymer even if the amount of a drug carried thereon is increased.
Patent Literature 1 discloses a compound in which a drug is bonded to a block copolymer of polyethylene glycol and polyaspartic acid without being mediated by a linker, wherein the drug shows water solubility by forming a micelle. Patent Literature 2 discloses a polymer derivative of camptothecins in which a side chain carboxy group of a block copolymer of polyethylene glycol and polyglutamic acid is ester bonded to a phenolic hydroxy group of the camptothecins.
Patent Literature 3 discloses a compound in which a side chain carboxy group of a block copolymer of polyethylene glycol and polyaspartic acid is bonded to an alcoholic hydroxy group of a taxane, and it is also described that a succinic acid monoamide structural moiety which constitutes the polyaspartic acid chain forms an imide bond and simultaneously the ester bond is cleaved to release the taxane. Patent Literature 4 discloses a compound linked with podophyllotoxin. Further, Patent Literature 5 also discloses a compound linked with combretastatins.